The present invention relates to spoked bicycle wheels of the type made of section comprising:
an outer circumferential wall and an inner circumferential wall, connected to each other by two side walls; and
means for supporting a plurality of nuts or nipples for tightening the wheel spokes, each nipple being designed to be screwed on a threaded end portion of a respective spoke.
According to the prior art, the inner circumferential wall of the rim has a plurality of holes, each having an edge that acts as a supporting seat for supporting the head of a respective nipple which is inserted into the hole and is screwed onto the threaded end of the respective spoke. The head of the nipple is therefore set in the internal space of the rim comprised between the outer circumferential wall and the inner circumferential wall. In the aforesaid known solution, the outer circumferential wall of the rim has a plurality of openings for insertion of the nipples, as well as for insertion of the tool for tightening the nipples.
More recently, however, the need has been felt for making spoked bicycle wheels with tubeless tires. In this case, the known solution described above is not usable in so far as the holes arranged on the outer circumferential wall of the rim would not enable air tightness of the chamber of the tire, which is under pressure, the said chamber being defined directly between the outer circumferential wall of the rim and the wall of the tire itself.
The purpose of the present invention is therefore to make a rim of the type referred to at the beginning of the present description that will, however, be usable also with a tubeless tire.
With a view to achieving the above purpose, the subject of the invention is a rim of the type specified above, characterized in that the aforesaid means for supporting the nipples comprise a plurality of nipple supports connected to the rim and arranged outside the section that forms the rim, each of the said nipple supports having a seat for supporting a respective nipple at least partially outside the section that forms the rim.
Thanks to the above characteristics, the rim according to the invention enables adoption of a tubeless tire in that the outer circumferential wall of the rim is without holes or openings, and is therefore perfectly airtight, whilst the nipples for tightening the spokes can be manoeuvred easily with any appropriate manoeuvring tool since they are arranged outside the section that forms the rim.
Again in accordance with the invention, each nipple support supports the respective nipple in a position that is at a slight distance from the inner circumferential wall of the rim in the direction of the axis of the rim. Preferably, each nipple support is made up of a bridge-type bracket which is set substantially in a radial plane containing the axis of the rim and has two opposite ends connected to the rim and a central part having an opening the edge of which functions as a supporting seat for the head of a respective nipple designed to be inserted into said opening.
According to a preferred embodiment, the edge of the opening provided in each nipple support is designed to co-operate with a corresponding surface of the head of the respective nipple in such a way as to leave the nipple the possibility of being oriented with its axis at least in a plane containing the axis of the rim. In addition, in the above-mentioned preferred embodiment each nipple support is connected to the rim in an articulated way about an axis that is substantially parallel to the axis of the rim.
Thanks to the aforementioned characteristics, when each nipple is assembled it can be readily adapted to the orientation that the respective spoke must assume with respect to the rim.
In one example of embodiment, the ends of the bridge-type bracket that makes up each nipple support are mounted on a pivot connected to the rim. This pivot is set so that it passes through two holes facing one another made in the two side walls of the rim in a radially more internal position with respect to the outer circumferential wall of the rim. Each pivot has its ends protruding outside of the side walls of the rim, and the respective nipple support has its ends articulated on said protruding ends of the pivot.
In an alternative embodiment, the inner circumferential wall of the rim has a circumferential groove or channel having two side walls, and each pivot of the nipple supports traverses also two holes set facing one another made in said side walls of said channel, the ends of the bracket that each forms a nipple support being articulated on the portion of the respective pivot that is set within said channel.
Again according to a further embodiment, the ends of the bridge-type bracket forming each nipple support are articulated by means of respective pivots to respective annular flanges protruding from the inner circumferential wall of the rim.
The way in which the articulation of each nipple support to the rim is obtained in accordance with the invention may, however, be different from the ones mentioned above by way of example.
Again in the case of the preferred embodiment of the invention, the bracket forming each nipple support has an asymmetrical configuration, with the central part of the bracket being inclined with respect to a direction parallel to the axis of the rim in such a way that the respective nipple is supported by said bracket, with its axis forming a camber angle with respect to the median plane orthogonal to the axis of the rim. The nipple supports are mounted on the rim in such a way as to form the aforesaid camber angle alternately on one side and on the other side of the median plane of the rim, it of course being possible to choose a different camber angle on each side and a camber angle different for the front wheel than the one for the rear wheel.
In the rim according to the invention, each nipple may be manoeuvred easily, since it is set outside the rim, by means of any suitable tool or wrench designed to engage on one side a portion of the nipple. For this purpose, the nipple has, in a way of itself known, a portion with a section shaped for engagement of the wrench.
The rim according to the invention thus enables assembly and tensioning of the spokes in a way similar to that adopted according to traditional techniques, even though the rim may have a continuous outer wall without any holes or openings.
The invention obviously relates both to the rim described above and to a bicycle wheel using said rim. Of course, the invention is suitable for making both front bicycle wheels and rear bicycle wheels since in the two cases the only difference lies in the number and arrangement of the spokes. On the other hand, as has been seen, the rim according to the invention enables each nipple to be oriented both in a plane containing the axis of the rim, thanks to the orientable support for the head of the nipple on the nipple-supporting bracket, and in a plane perpendicular to the axis of the rim, thanks to the articulated connection of the nipple-supporting bracket to the rim.